Linear motion zero adjuster

ABSTRACT

A zero adjust mechanism includes a shaft member arranged for axial movement within a tubular housing, with one end of said shaft extending out from one end of the housing and being adapted to be coupled to a meter movement. A bellows surrounds the portion of the shaft within the housing and a drive means is coupled to the other end of the shaft for imparting axial movement thereto in response to rotative movement of the drive means.

United States Patent [191 Makovec 1 July 3, 1973 [54] LINEAR MOTION ZEROADJUSTER 3.216264 ll/ I965 Lloyd 74/l8.2 [75] Inventor: znldrew M.Makovec, Livingston, Primary sxaminer charles J. Myhre AssistantExaminer- F p. Shoemaker Assigneer Weston Instruments, eAttorney-William R. Sherman, Jerry M. Presson and Leonard R. Fellen etal. [22] Filed: Aug. 12, 1971 [57] ABSTRACT [21] Appl' 171,232 A zeroadjust mechanism includes a shaft member arranged for axial movementwithin a tubular housing, [52] US. Cl. 74/ 18.2 with one end of SaidShaft extending out from end 51] Int. Cl Fl6j 15/52 of the housing andbeing adapted to be coupled to a 58 Field of Search 74/182, 18, 89.15meter movement A bellows Surrounds the portion of I the shaft within thehousing and a drive means is cou 5 References Cited pled to the otherend of the shaft for imparting axia l UNITED. STATES PATENTS movementthereto in response to rotative movement of 239 036 the drive means.

8/1960 Ellis 74/18.2 x

4 Claims, 5 Drawing Figures PATENTEDJULQ 197a SHEET 2 [IF 2 LINEARMOTION ZERO ADJUSTER This invention relates to hermetically sealedinstruments and more particularly to a device for transmitting linearmotion to a mechanism inside a hermetically sealed case.

The invention described herein was made in the performance of work undera NASA contract and is subject to the provisions of Section 305 of theNational Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435; 42 U.S.C. 2457). g In certain instruments which include a sensitivemeasuring or indicating mechanism, for example, it is desirable that themechanism be hermetically sealed against contamination from thesurrounding media. Very often the construction of such instruments mustprovide a means for externally adjusting the sealed mechanism within. Inaddition, it is often desirable that the externally accessible adjustingmeans itself be restrained against lengthwise movement and the drivenadjusting shaft be given a linear non-rotative motion. Further, spaceconsiderations may also limit the extent or degree of movement of theadjusting means as well as prohibit the use of complicated. linkages inassociation therewith.

An object of the present invention is to provide an improved adjustingdevice for transmitting linear motion to a mechanism inside ahermetically sealed housing.

Another object of the present invention is to provide an adjustingdevice free of gears or unduly complicated linkages, comprising fewcomponents and which is easily adaptable for miniaturization andmodification according to the size of the mechanism for which it is tobe used.

Briefly described, the apparatus of the invention includes a shaftmember arranged for axial movement within a tubular housing, with oneend of said shaft extending out from one end of the housing and beingadapted to be coupled to a meter movement. A bellows surrounds theportion of the shaft within the housing and a drive means is coupled tothe other end of the shaft for imparting axial movement thereto inresponse to rotative movement of the drive means.

The novel features which are considered to be characteristic of theinvention are set forth with particularity in the appended claims. Theinvention itself, how- 'ever, both as to its organization and method ofoperation as well as additional objects and advantages thereof will bestbe understood from the following description when read in connectionwith the accompanying drawings in which:

FIG. 1 is a top plan view ofa zero adjust means in accordance with thepresent invention as utilized in association with a panel meter;

FIG. 2 is perspective view of thezero adjust means and showing thecoupling thereof to a meter mechanism;

FIG. 3 is a front sectional elevation view of the zero adjust meanstaken along line 3--3 of FIG. 1;

FIG. 4 is a left side view of the zero adjust means; and

FIG. 5 is a right side view of the zero adjust means.

Referring now to the drawing and to FIG. I thereof, the adjustingapparatus 10 of the invention is shown in use as a zero adjust meansfora panel type meter housed in a hermetically sealed casing indicatedgenerally at 12. As shown more particularly in the perspecassembly.

tive view of FIG. 2, the adjusting apparatus includes a tubular housingmember 14, a push rod or shaft 16 arranged for linear travel in and outof the housing memher at one end 18 thereof, an'end cap member 20 seatedin one end of the housing 18, a flexible bellows 22 received within thehousing and surrounding the shaft 16 therein and which serves as a meansfor isolating the shaft from the environment an adjusting screw member24 together with associated end thrust and retainer washers 26 and 28,and a cantilevered arm means 30 for coupling the longitudinal movementof the shaft 16 into a corresponding rotative movement of a zero adjustor centering spring 32 for the meter pointer 34. v

With reference now to FIGS. 3, 4, 5 and FIG. 2, the outgoing end portionof the shaft 16 will be seen to be cut away to form a flat surface 36and shoulder abutment 38. The other end of the shaft 16 is formed withtwo annular step portions 40 and 42 of successively lesser diameters.Also provided in-this end of the shaft is an axially extending bore oraperture 44 threaded to receive the adjusting screw 24 in the assemblyof the apparatus. 7

The housing member 14 is generally cylindrical in shape and includes atone end thereof, a peripheral shoulder 46 surrounding an enlarged screwthreaded opening 48. Continuing from the opening 48 is a bore 50 of aslightly lesser diameter, extending axially along the housing member andmerging into a smaller diameter opening 52 at the other end of thehousing. An annular shoulder or lip 54 is formed inside the housingsurrounding the opening 52 and provides a retaining means for componentparts of the adjusting apparatus that are inserted through the opening48 in the housing one end as will hereinafter be described.

The end cap member 20 received within the housing is generallycylindrical in shape and includes an annular flange portion 56intermediate of two circular boss end portions 58 and 60. As best shownin FIG S. 2 and 3, formedin one end of the cap member 20 is asemicircular keyway or aperture 62 conforming to and for rehousing bore50 and the key way end boss 58 to be captively seated within the housingend opening 52, with I the flange 56 abutting the shoulder 54 in thehousing.

Assembly of the apparatus of the invention is asfollows.

The bellows member 22 is first positioned on the shaft 16 and coaxialtherewith so that one end 64 thereof is seated on the lower step portion42 at the end of the shaft that receives the adjusting screw 24. Thisend of the bellows is then hermetically sealed to the shaft step portion42 in any desirable manner to pro vide a leakproof, non-rotatableconnection. While this connection is preferably made by brazing with ahigh temperature metal or alloy, it will be understood that othersealing methods, as for example, soldering or the use of an epoxy may beemployed in this stage of the The end cap 20 is next slid over the shaftflat end 36 and movedthere along until the other end 66 of the bellowsis received over the end boss portion 60 and seated up against theflange 56. As was heretofore noted, the aperture 62 in the end cap 20 iskeyed to conform to the flat end portion 36 of the shaft such that theend cap is free to slide back and forth along the length of the flat endportion of the shaft, but is constrained against rotative moment aroundthe shaft. The bellows end 66 is then hermetically sealed to the endboss 60 of the cap 20 as by brazing or otherwise.

Next in the assembly of the adjusting apparatus, the bellows and shaftassembly is inserted into the housing bore 50 through the enlarged andthreaded opening 48 and moved along the bore length to a positionwherein the keyed boss end 58 is seated within the housing end opening52, with a surface of the cap flange 56 abutting the annular shoulder 54around the opening 52. With the bellows and shaft assembly thus placed,the boss 58 on the end cap is then fastened via some sealing means tothe housing end portion so as to form a part thereof and provide aleakproof juncture therewith. It should be noted, that in this sealingoperation, soldering or the use of an epoxy is preferred over brazing.The reason for this is that epoxy and solder materials generally have alower melting point than brazing materials and as such in sealing theend cap to the housing thereis less likelihood of loosening ordisturbing the other brazing joints in the apparatus.

Next in the assembly, a thrust washer 26 is inserted into the housingand seated on the back end surface of the shaft. The adjusting screw isthen inserted through the washer 26 and into the complimentary threadedbore 44 in the shaft. To close off the opening 48 a screw threadedretainer washer 28 is provided.

It will be noted, and as shown in the Figures, that the adjusting screw24 is capped by an integrally formed annular flange 68 and a slottedhead portion 70. The retainer washer 28 is formed with an annular recess72 generally conforming to the adjusting screw flange portion 68 and acoaxial aperture 74 for receiving the slotted head portion 70 of theadjusting screw.

The thrust washer 26 provides a bearing surface acting against the backside of the screw flange, and also functions to prevent inward movementof the screw. The retainer washer is screwed into the threaded openingin the housing such that the screw flange portion is seated within therecess 72 and the slotted head 70 is received in the aperture 74. Tofacilitate insertion of the washer 28 into the housing, two dimpledrecesses 76 and 78 (FIG for receiving a spanner wrench may be provided.Aside from closing the opening 48, the retainer washer functions toprevent outward movement of the screw during adjustment. Thus the twowashers, i.e. the thrust and retaining washers thereby serve to hold thescrew captive and prevent any longitudinal movement thereof.

To further lock the retainer washer in place as a closure for thehousing opening 48, the peripheral threads of the housing opening may beupset in several places 80 as by staking or alternatively by the use ofan epoxy or some other locking compound.

In the preferred embodiment illustrated, the assembled adjustingapparatus is installed through a suitable opening in an end wall of acasing which houses a meter mechanism with which the apparatus of theinvnetion is to be utilized as a zero adjust means. In the embodimentillustrated, the adjusting apparatus housing 14 is inserted through anopening in a wall of a meter casing '12 such that the peripheralshoulder 46 of the housing 14 abuts the casing wall. The housingshoulder is then hermetically sealed to the casing wall to provide aleak tight connection. Thereafter, the arm means 30 is connected fromthe outwardly extending portion of the shaft 16 to the meter mechanismcentering spring 32. More particularly, and as shown in FIG 2, fasteningmeans in the form of a shouldered washer 82 and screw 84 is insertedthrough an elongated opening 86 in the arm member 30 and second washer88 and then screwed into a tapped hole 90 in the outwardly extending endportion of the shaft 16. The other end of the arm is coupled eitherdirectly or by means of a clutch arrangement 92 wherein the arm end iscoupled to a disc 94, which includes a depending tab projection 96 towhich the outer end of the spiral meter spring 32 has been connected oraffixed. The meter apparatus complete with the zero adjusting means ofthe invention can then be hermetically sealed in an outer casing toprovide a complete sealing of the meter from an outside environment.

The operation of the zero adjust apparatus should be apparent from theFIGS. 1 and 2. By turning the screw head clock-wise for example, theshaft 16 will be caused to move into the housing 14 thereby pivoting thearm member 30 also in a clock-wise direction as viewed in FIG. 2 suchthat the coupled spring outer end is also moved in a clock-wisedirection thereby to adjust it as desired. Similarly, rotation of theadjusting screw head of the adjusting means in a counter clockwisedirection will produce a counter clockwise adjustment or rotation of thespiral spring end associated with the meter movement. It will also beapparent that with adjusting apparatus of the present invention asherein described, rotation of the adjusting screw occurs in effect thezero correction desired.

With the apparatus constructed as described, the apparatus of theinvention is free of any complicated linkages or gears and is easilyadaptable for miniaturization and modification according to the size ofthe mechanism for which it is to be used.

What is claimed is:

l. A linear motion hermetically sealed zero adjuster apparatus formounting in the case of a sealed instrument including in combination:

an elongated shaft member;

a tubular housing receiving therein for axial movement one end of saidshaft member, the other end thereof extending outwardly from one end ofsaid housing and being adapted to be coupled to the instrument withinthe case;

a bellows positioned within said housing in surrounding relation andhaving one end hermetically sealed to the one end of said shaft member;

means coupling the other end of said bellows to said tubular housing andproviding a hermetic seal therewith while allowing for axial movement ofsaid shaft;

drive means coupled to said shaft member for imparting axial movementthereto in response to rotative movement of said drive means, a portionof said drive means being exposed through the other end of said housingto the exterior of said instrument case for rotary movement thereof;

. retaining means mounted on said housing for restraining said drivemeans against axial movement while allowing for rotary movement thereof.

2. The combination as defined in claim 1 wherein:

said drive means includes a screw member having a slotted head portionseated on a surrounding flange portion, and a threaded shank portion,

said shaft member one end having an axially extending threaded borereceiving the shank portion of said drive-means, the flange portion ofsaid drivemeans being captively coupled to said retainer means so as torestrain said screw member against axial movement in response torotation thereof.

3. The combination as defined in claim 2 wherein said other end of thehousing includes stop means and wherein said retainer means includes:

a first washer seated within the other end of said housing and having anaperture which receives said screw member but is smaller than saidflange portion thereof, said stop means engaging said first washer toprevent axial movement thereof toward said one end of the housing, saidfirst washer acting as a bearing surface against the side of said flangeportion facing said one end of the housing to limit axial movement ofsaid flange portion and hence of of said screw member toward said oneend of the tubular housing;

a second washer circumferentially surrounding said flange portion andhaving a portion facing the side of said flange portion which faces saidother end of the housing and an aperture therein receiving the slottedhead portion of said screw member; and

means for fixing the position of said second washer within said housingother end and inhibiting axial movement thereof.

4. The combination as defined in claim 3 wherein the one end of saidhousing is formed with an inner lip portion surrounding an openingtherein and wherein said coupling means includes an apertured cap membercomprising a flange portion disposed between two annular bosses one ofwhich is received within said end opening and hermetically sealed tosaid housing with said cap member flange portion being seated againstsaid housing lip portion, the other end of said bellows being receivedaround and hermetically sealed to said other boss, the other end of saidshaft member being slidably received through said cap member aperture.

1. A linear motion hermetically sealed zero adjuster apparatus formounting in the case of a sealed instrument including in combination: anelongated shaft member; a tubular housing receiving therein for axialmovement one end of said shaft member, the other end thereof extendingoutwardly from one end of said housing and being adapted to be coupledto the instrument within the case; a bellows positioned within saidhousing in surrounding relation and having one end hermetically sealedto the one end of said shaft member; means coupling the other end ofsaid bellows to said tubular housing and providing a hermetic sealtherewith while allowing for axial movement of said shaft; drive meanscoupled to said shaft member for imparting axial movement thereto inresponse to rotative movement of said drive means, a portion of saiddrive means being exposed through the other end of said housing to theexterior of said instrument case for rotary movement thereof; retainingmeans mounted on said housing for restraining said drive means againstaxial movement while allowing for rotary movement thereof.
 2. Thecombination as defined in claim 1 wherein: said drive means includes ascrew member having a slotted head portion seated on a surroundingflange portion, and a threaded shank portion, said shaft member one endhaving an axially extending threaded bore receiving the shank portion ofsaid drive-means, the flange portion of said drive-means being captivelycoupled to said retainer means so as to restrain said screw memberagainst axial movement in response to rotation thereof.
 3. Thecombination as defined in claim 2 wherein said other end of the housingincludes stop means and wherein said retainer means includes: a firstwasher seated within the other end of said housing and having anaperture which receives said screw member but is smaller than saidflange portion thereof, said stop means engaging said first washer toprevent axial movement thereof toward said one end of the housing, saidfirst washer acting as a bearing surface against the side of said flangeportion facing said one end of the housing to limit axial movement ofsaid flange portion and hence of of said screw member toward said oneend of the tubular housing; a second washer circumferentiallysurrounding said flange portion and having a portion facing the side ofsaid flange portion which faces said other end of the housing and anaperture therein receiving the slotted head portion of said screwmember; and means for fixing the position of said second washer withinsaid housing other end and inhibiting axial movement thereof.
 4. Thecombination as defined in claim 3 wherein the one end of said housing isformed with an inner lip portion surrounding an opening therein andwherein said coupling means includes an apertured cap member comprisinga flange portion disposed between two annular bosses one of which isreceived within said end opening and hermetically sealed to said housingwith said cap member flange portion being seated against said housinglip portion, the other end of said bellows being received around andhermetically sealed to said other boss, the other end of said shaftmember being slidably received through said cap member aperture.